Today,the solution to the problem is so common that it is difficult to understand that there was a problem at all.

VOA: special.2010.07.14

This is a common problem in gene therapy.

这是基因治疗中的通病

耶鲁公开课 - 生物医学工程探索课程节选

These are going to be fairly common-sense definitions, but they're important, and when you get to a problem set, really nailing down what the system is, not more, nor less, in terms of the amount of stuff, that's part of the system, it's going to be often very crucial.

这些是,很常识性的定义，但是很重要，当你要解决问题时，务必要搞清楚系统是什么，它包含多少物质，不能多也不能少，这往往,是非常重要的。

麻省理工公开课 - 热力学与动力学课程节选

And this design reduced feedback, a noise problem common with acoustic guitars.

VOA: special.2009.09.27